Curing agent composition for epoxy resins, epoxy resin composition and use thereof

ABSTRACT

An epoxy resin composition comprising an epoxy resin (A), a curing agent (B) and a curing accelerator (C), wherein the curing agent (B) is a phenol compound having two or more hydroxyl functional groups or a compound obtained by esterification of the phenol compound or a mixture of these compounds, and the curing accelerator (C) is a salt of a phosphazenium compound represented by a formula (I): 
                 
 
(wherein R 1 s each represent a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms or an aryl or aralkyl group having 6 to 10 carbon atoms and may be all the same or different from one another; and Z −  represents a halogen anion, hydroxy anion, alkoxy anion, aryloxy anion or carboxy anion).

TECHNICAL FIELD

The present invention relates to a semiconductor device obtained bysealing a semiconductor integrated circuit with an epoxy resin. Thepresent invention provides an epoxy resin composition which has variousphysical properties satisfactory to make the composition usable for itsapplication, e.g., low hygroscopicity and excellent melt-flowability ofthe resin composition in particular and which provides overall crackingresistance. Further, the present invention also relates to an epoxyresin composition comprising a catalyst which causes a functional groupsuch as a phenolic hydroxyl group or an ester group to react with anepoxy group quickly, and a cured product of the epoxy resin composition.

BACKGROUND ART

Heretofore, integrated circuits (IC) and large scale integrated circuit(LSI) have been protected from malfunctions caused by dirt, dust, heat,moisture or light in an external atmosphere by sealants for protectingthem in order for the circuits to be actually used.

In recent years, the sealants have been gradually shifted from sealingwith metal materials and ceramic materials to sealing with resins, andat present, epoxy resin sealants are predominantly used.

In particular, in view of balance between costs and physical properties,epoxy resin compositions using a phenol resin as a curing agent are usedin large quantities. The sealants using these epoxy resin compositionshave problems such as improvement in mechanical properties as well as:

-   -   (i) suppression of crack occurrence at the time of reflow        soldering, and    -   (ii) improvement in electrical reliability.

Generally, the occurrence of cracks at the time of reflow soldering in(i) is assumed to be caused by water in the resin which expands sharplywhen exposed to high temperatures at the time of reflow soldering.Hence, means for solving the problem is largely focused on control ofmoisture absorptivity of the resin, and mechanical strength and adhesionof the resin to metal are also involved in the means on the whole.

However, since a reaction between an epoxy group and a hydroxyl group isa reaction which always produces a hydroxyl group as shown by thefollowing reaction formula (1), hydrophilicity becomes higher due to thehydroxyl group, and even if a basic skeleton is rendered hydrophobic, areduction in the moisture absorptivity as a whole is limited.Reaction Formula (1):

(wherein A represents an epoxy residue, and B represents a phenolresidue).

As a technique for solving these problems, a technique disclosed in, forexample, EP 959088 which uses a phosphine oxide derivative as a curingaccelerator has been studied.

Since an epoxy resin composition using the accelerator is cured by useof the phenol resin, moisture absorptivity is almost the same as thatwhen triphenylphosphine or imidazole which is a commonly usedaccelerator is used. As for improvements in other physical properties,however, a significant improvement in cracking resistance is seen.

Further, its curing behavior has a significantly great merit from anindustrial standpoint in that initial curing takes long time andcomplete curing takes short time.

Meanwhile, with respect to the improvement in electrical reliability in(ii), the following problems exist.

(ii)-1: As a side reaction at the time of curing, epoxyhomopolymerization occurs in some portions. As a result, hydroxyl groupsof the phenol resin become excessive, so that the composition has poormoisture resistance and electric characteristics. Further, since theepoxy homopolymerized portions and the excessive phenol resin portionsexist in addition to an essential epoxy-phenol resin network, thecomposition also has poor mechanical properties.

(ii)-2: Mainly due to corrosion of metal portions and current leakage ofa semiconductor which are caused by incorporation of free ions, halogenions in particular, the electrical reliability is adversely affected.

Of these, the ion impurities in (ii)-2 are a problem of purification andpurity of the epoxy resin in particular and are not intrinsic. As forthe problem of (ii)1, modification of the resin and/or control of theside reaction can cause the epoxy resin composition to fully exhibitphysical properties inherent in the epoxy resin composition.

These problems indicated by (ii)-1 and (ii)-2 influence a technique tobe described hereinafter.

That is, for the purpose of reducing the moisture absorptivity of theresin in the foregoing problem (i), a reaction between an epoxy groupand an ester group as disclosed in Japanese Patent Application Laid-OpenNo. 53327/1987 applied by Nishikubo et al. has been proposed.

In the publication, a quaternary onium salt and a crown ether complexare set forth as preferable catalysts, and in a paper [Addition Reactionof Epoxy Compound with Ester and Its Application to Synthesis ofPolymer, Synthetic Organic Chemistry, Vol. 49, pp. 218 to 233 (1991)] byNishikubo et al., yields when the catalysts are used as unit reactionsare specifically described. According to the paper, although the highestyield is 91% which is a yield when tetrabutylammonium chloride is used,the yields are generally low.

It is needless to say that if an ionic compound such as the quaternaryonium salt and the crown ether complex remain in a resin used as asealant for a semiconductor integrated circuit, this means that theionic impurities described in the foregoing (ii)-1 are added as a curingaccelerator, thereby causing undesirable results such as an electricalshort circuit as well as corrosion of metal portions in contact with theimpurities, and these undesirable results and the corrosion in turncause serious defects in products.

Meanwhile, in a general addition reaction between an epoxy resin and aphenol resin, a phosphine such as trialkylphosphine or triarylphosphine,imidazole, a tertiary amine or the like is used as a catalyst, andparticularly for sealing a semiconductor, imidazole and the phosphinesare often used. When these catalysts are used in the reaction between anepoxy group and an ester group, imidazole having reaction activity isliable to cause epoxy homopolymerization which is the foregoing sidereaction, and the problem of the foregoing (ii)-2 is remarkable. On theother hand, although the phosphines do not have these problems, theyhave slow curing speed and provide substantially no cured product.

Therefore, the idea of preparing a curing agent for an epoxy resin byesterifying some or all hydroxyl groups of the phenol resin as thecuring agent for the purpose of obtaining lower hygroscopicity hasheretofore not been implemented because no effective curing catalyst hasbeen available.

Under such circumstances, in recent years, a phosphazene catalyst forcuring an ester group and an epoxy group effectively has been proposed.More specifically, it has been found that the phosphine oxide derivativedisclosed in the foregoing EP 959088 is effective for an epoxy-estercuring reaction. Japanese Patent Application Laid-Open No. 80049/2000discloses its production and high activity in a unit reaction between anepoxy group and an ester group (reaction between monofunctionalcompounds), and Japanese Patent Application Laid-Open No. 349662/1999discloses its application to a sealant.

However, it has been found that due to hydrolytic properties of thephosphine oxide derivative, if a cured resin absorbs water with thederivative contained therein and is exposed to high temperatures as inreflow soldering, the derivative is decomposed easily, and electricconductivity increases significantly. That is, the phosphine oxidederivative is not suitable as a sealant in some cases.

Further, a phosphazenium compound which is a curing catalyst is alreadydisclosed in Japanese Patent Application Laid-Open No. 77289/1998 whichalso discloses that the phosphazenium compound exhibits high activity ina unit reaction between an epoxy group and an ester group.

In consideration of these facts, it may seem to be easy to use thephosphazenium compound together with an epoxy resin having two or morefunctional epoxy groups and a phenol resin having two or more functionalgroups or an ester derivative thereof as a thermosetting resin. However,it is generally known that a basic reaction does not necessarily exhibitthe same level of reaction activity under a reaction in a polymer.

That is, it must be considered in the case of a three-dimensionalcrosslinking curing reaction that as three-dimensional crosslinkingproceeds, skeletal steric hindrance occurs due to bondings occurring inthe vicinity of functional groups and molecules are fixed along withcuring, so that the curing reaction may not proceed easily.

When the ionic phosphazenium compound is used as a catalyst, it isconceivable that the compound may not be a favorable catalyst for asealant with respect to which control of inclusion of ionic substancesis generally strict.

Under the circumstances, in the present invention, an epoxy resincomposition suitable for use as a sealant, a cured product thereof, anda curing agent composition for the epoxy resin composition.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a composition forcausing a phenol resin for providing a cured epoxy resin resin havinglow hygroscopicity and excellent electric characteristics or an esterderivative thereof resulting from esterification of some or all hydroxylgroups of the phenol resin with an aliphatic acyl group or aromatic acylgroup to react with an epoxy resin or compound effectively. Inparticular, an object of the present invention is to provide an epoxyresin composition for a semiconductor sealant which is excellent incracking resistance and electric characteristics, a cured product of thecomposition, a semiconductor device produced by use of the composition,and a curing agent composition for an epoxy resin.

The present inventors have found that such objects can be achieved by aspecific compound comprising a stable cation and a counter anion andhave completed the present invention on the basis of this finding.

That is, the present invention is a curing agent composition for anepoxy resin which comprises a compound as a curing agent (B) which isselected from the group consisting of the following (B1) to (B3):

-   -   (B1) a phenol compound having two or more hydroxyl functional        groups,    -   (B2) a compound in which a hydroxyl group of a phenol compound        having two or more hydroxyl functional groups is esterified with        an acyl group, and    -   (B3) a mixture of the above compounds (B1) and (B2),        and a salt of a phosphazenium compound as a curing        accelerator (C) which is represented by the following formula        (I):        (wherein R¹s each represent a hydrogen atom, a linear, branched        or cyclic alkyl group having 1 to 10 carbon atoms or an aryl or        aralkyl group having 6 to 10 carbon atoms and may be all the        same or different from one another; and Z⁻ represents a halogen        anion, hydroxy anion, alkoxy anion, aryloxy anion or carboxy        anion).

Further, the present invention is an epoxy resin composition comprising:

-   -   (A) an epoxy resin having two or more epoxy groups in a        molecule,    -   (B) a curing agent, and    -   (C) a curing accelerator,        wherein the curing agent (B) is a compound selected from the        group consisting of the following (B1) to (B3):    -   (B1) a phenol compound having two or more hydroxyl functional        groups,    -   (B2) a compound in which a hydroxyl group of a phenol compound        having two or more hydroxyl functional groups is esterified with        an acyl group, and    -   (B3) a mixture of the above (B1) and (B2),        and the curing accelerator (C) is a salt of a phosphazenium        compound which is represented by the above formula (I).

Still further, the present invention is a cured epoxy resin obtained byheat-curing the foregoing epoxy resin composition.

Still further, the present invention is a semiconductor device obtainedby sealing a semiconductor integrated circuit by use of the foregoingepoxy resin composition.

Still further, the present invention is an epoxy resin compositioncomprising:

-   -   (A) an epoxy resin having two or more epoxy groups in a        molecule,    -   (B) a curing agent, and    -   (C) a curing accelerator,        wherein the curing agent (B) is a compound selected from the        group consisting of the following (B1) to (B3):    -   (B1) a phenol compound having two or more hydroxyl functional        groups,    -   (B2) a compound in which a hydroxyl group of a phenol compound        having two or more hydroxyl functional groups is esterified with        an acyl group, and    -   (B3) a mixture of the above (B1) and (B2),        and the curing accelerator (C) is a salt comprising a stable        cation and a counter anion.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a graph showing the curing behavior of an epoxy resincomposition when CURELASTOMETER is used.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, as a curing accelerator (C), a salt comprisinga stable cation and a counter anion typified by a salt of aphosphazenium compound which is represented by the foregoing formula (1)is used, and as the curing agent (B), a compound selected from the groupconsisting of the following (B1) to (B3)is used:

-   -   (B1) a phenol compound having two or more hydroxyl functional        groups,    -   (B2) a compound in which a hydroxyl group of a phenol compound        having two or more hydroxyl functional groups is esterified with        an acyl group, and    -   (B3) a mixture of the above (B1) and (B2),

When the mixture (B3) is used, a mixing ratio of the compound (B1) andthe compound (B2) is arbitrary and should be determined by determiningdesired physical properties of a cured product according to targetapplication and grade.

That is, hygroscopicity lowers as the number of ester groups increases,while adhesion to metal such as a lead frame improves as the number ofhydroxyl groups increases, whereby mechanical strength is improved.

In the epoxy resin composition of the present invention, when thephosphazenium compound of the formula (1) is used as the essentialaccelerator, a reaction between an epoxy group and an ester group whichhas conventionally been unable to proceed to a sufficient degree canfully proceed as a curing reaction, a problem of the side reaction ofthe foregoing problem (ii) can be solved, and a cured product which isexcellent particularly in flexibility, moisture resistance, crackingresistance and electric characteristics can be provided, as comparedwith when conventional imidazole or triphenylphosphine is used as theaccelerator.

Further, even when an unesterified phenol resin is used, heat resistanceis improved and complete curing becomes fast, as compared with when theconventional accelerator is used.

In addition, a resin composition prepared by adding an organic and/orinorganic filler(s) (D) to the epoxy resin composition exhibitsextremely excellent performance as a sealant for a semiconductorintegrated circuit.

Meanwhile, as compared with the aforementioned prior art using aphosphine oxide derivative as a curing accelerator, electricalreliability as electrical and electronic products improves.

That is, while the phosphine oxide derivative has hydrolytic propertiesas a compound and has a problem with respect to electrical reliability,the phosphazenium compound used in the present invention is stable.Thus, the difference in electrical reliability occurs.

That is, the epoxy resin composition of the present invention ispreferably an epoxy resin composition comprising:

-   -   (A) an epoxy compound or resin having two or more functional        groups,    -   (B) a phenol compound or resin having two or more hydroxyl        functional groups, 0 to 100 mol % of hydroxyl groups of which        have been esterified by acyl groups, or an ester derivative        thereof, and    -   (C) a phosphazenium compound represented by the above        formula (1) as a curing accelerator as essential components.

Hereinafter, the phosphazenium compound represented by the formula (1)which is used in the present invention will be described.

In the formula (1), substituents R¹s each represent a hydrogen atom, alinear, branched or cyclic alkyl group having 1 to 10 carbon atoms or anaryl or aralkyl group having 6 to 10 carbon atoms and may be all thesame or different from one another.

Illustrative examples of R¹ include a hydrogen atom; a linear, branchedor cyclic alkyl group such as a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, an s-butyl group,a t-butyl group, a 1-pentyl group, a 2-pentyl group, a 3-pentyl group, a2methyl-1-butyl group, an isopentyl group, a t-pentyl group, a3-methyl-2-butyl group, a heopentyl group, an n-hexyl group, a4-methyl-2-pentyl group, a cyclopentyl group, a cyclohexyl group, a1-heptyl group, a 3-heptyl group, a 1octyl group, a 2-octyl group, a2-ethyl-1-hexyl group, a nonyl group or a decyl group; an aryl groupsuch as a phenyl group; and an aralkyl group such as a toluyl group, abenzyl group, a 1-phenylethyl group or a 2-phenylethyl group.

Of these, an aliphatic hydrocarbon group having 1 to 6 carbon atoms suchas a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group or a cyclohexyl group is preferable, and themethyl group and the ethyl group are more preferable.

In the formula (1), Z⁻ represents a halogen anion, hydroxy anion, alkoxyanion, aryloxy anion or carboxy anion.

In addition, any anions can be used as long as they do not inhibit theeffect of the present invention.

Illustrative examples of Z⁻ include a halogen anion such as a fluorineanion, a chlorine anion, a bromine anion or an iodine anion; a hydroxyanion; an alkoxy anion derived from an alcohol such as methanol,ethanol, n-propanol, isopropanol, allyl alcohol, n-butanol, s-butanol,t-butanol, cyclohexanol, 2-heptanol, 1-octanol, 1-decanol oroctahydronaphthol; an aryloxy anion derived from an aromatic hydroxycompound such as phenol, cresol, xylenol, naphthol, 2-methyl-1-naphtholor 9-phenanthrol; and a carboxy anion derived from a carboxylic acidsuch as formic acid, acetic acid, propionic acid, butyric acid,isobutyric acid, caproic acid, decanecarboxylic acid, oleic acid,benzoic acid or naphthoic acid.

Of these, the hydroxy anion; an alkoxy anion derived from an alcoholhaving 1 to 4 carbon atoms such as methanol, ethanol, n-propanol,isopropanol, n-butanol, s-butanol or t-butanol; an aryloxy anion derivedfrom an aromatic hydroxy compound having 6 to 8 carbon atoms such asphenol or cresol; and a benzoyloxy anion derived from benzoic acid arepreferable. More preferable are the hydroxy anion, a methoxy anion, aphenoxy anion and the benzoyloxy anion. The most preferable is thehydroxy anion.

These phosphazenium compounds may be used solely or in admixture of twoor more.

These phosphazenium compounds can be synthesized in accordance with amethod disclosed in Japanese Patent Application Laid-Open No. 77289/1998or a similar method.

In the epoxy resin composition of the present invention, the curingaccelerator (C) is used in an amount of 0.001 to 25 wt % (0.001 to 25g/100 g), preferably 0.01 to 15 wt %, more preferably 0.1 to 8 wt %,based on 100 wt % of a resin component (total of the epoxy resin (A) andthe curing agent (B)).

Further, in the epoxy resin composition of the present invention,together with the phosphazenium compound, a generally used, knownaccelerator other than the phosphazenium compound, such as imidazole,e.g., 2-methylimidazole or a phosphine, e.g., triphenylphosphine, may beused in an amount of 0.5 to 500 wt % of the phosphazenium compound. Thecharacteristics of the present invention are exhibited readily when theamount is not higher than 500 wt % (five-fold equivalent).

The phosphazenium compound has almost no deliquescent properties. Evenin the following preparation of the composition, it can be handled undera normal atmosphere as in the case of other compounds.

In the epoxy resin composition of the present invention, the epoxy resinas the component (A) is an epoxy resin having two or more epoxy groupsin a molecule. As the epoxy resin (A), a variety of conventionally knownepoxy resins can be used regardless of molecular structure, molecularweight and the like as long as they can be cured by a variety of curingagents as will be described later.

Firstly, preferable examples of the epoxy resin (A) include a novolacepoxy resin represented by the following formula (II), aphenol-dicyclopentadiene-type epoxy resin represented by the followingformula (III), a phenol-aralkyl-resin-type epoxy resin represented bythe following formula (IV), a naphthol-aralkyl-resin-type epoxy resinrepresented by the following formula (V), abiphenol-type-epoxy-containing epoxy resin represented by the followingformula (VI) or a bisphenol-type-epoxy-containing epoxy resinrepresented by the following formula (VII):

(wherein R²s each represent a hydrogen atom, a methyl group or an ethylgroup, and n which is the number of recurring units represents aninteger of 0 to 50, its average being within a range of 0 to 15),

(wherein R³s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group, and n whichis the number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15),

(wherein R⁴s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group, and n whichis the number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15),

(wherein R⁵s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms, a phenyl group or a glycidylether group, and n which is the number of recurring units represents aninteger of 0 to 50, its average being within a range of 0 to 15),

(wherein R⁶s each represent a hydrogen atom, a methyl group or an ethylgroup and may be all the same or different from one another), and

(wherein R⁷s each represent a hydrogen atom, an alkyl group having 1 to10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms, an arylgroup having 6 to 10 carbon atoms, an aryloxy group having 6 to 10carbon atoms or halogen and may be all the same or different from oneanother, and Y represents an alkylidene having 1 to 10 carbon atoms, analkylene having 2 to 10 carbon atoms, a cycloalkylidene having 3 to 10carbon atoms, a cycloalkylene having 3 to 10 carbon atoms or a divalentgroup such as —O—, —CO—, —CO₂—, —S—, —SO—or —SO₂—).

As the epoxy resin (A), a variety of conventionally known epoxy resinscan be used. For example, an epoxy resin synthesized from a variety ofnovolac resins including epichlorohydrin and bisphenol, an alicyclicepoxy resin or an epoxy resin incorporating a halogen atom such aschlorine or bromine can be used. The above epoxy resins can be usedsolely or in admixture of two or more.

Preferable examples thereof include dihydroxybenzenes such as catechol,resorcin and hydroquinone, dihydroxynaphthalenes such as1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene,1,6-dihydroxynaphthalene, 2,5-dihydroxynaphthalene and2,6-dihydroxynaphthalene, epoxy resins obtained by epoxidating phenolichydroxyl groups of a phenol novolac resin represented by the followingformula (XIV):

(wherein R¹⁴s each represent a hydrogen atom, a methyl group or an ethylgroup, and n which is the number of recurring units represents aninteger of 0 to 50, its average being within a range of 0 to 15),

-   -   a phenol-dicyclopentadiene resin represented by the following        formula (XV):        (wherein R¹⁵s each represent a hydrogen atom, a halogen atom, a        linear, branched or cyclic aliphatic alkyl group having 1 to 8        carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a        phenyl group, and n which is the number of recurring units        represents an integer of 0 to 50, its average being within a        range of 0 to 15),    -   a phenol aralkyl resin represented by a formula (XVI):        (wherein R¹⁶s each represent a hydrogen atom, a halogen atom, a        linear, branched or cyclic aliphatic alkyl group having 1 to 8        carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a        phenyl group, and n which is the number of recurring units        represents an integer of 0 to 50, its average being within a        range of 0 to 15),    -   a naphthol aralkyl resin represented by a formula (XVII):        (wherein R¹⁷s each represent a hydrogen atom, a halogen atom, a        linear, branched or cyclic aliphatic alkyl group having 1 to 8        carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a        phenyl group or a hydroxyl group, and n which is the number of        recurring units represents an integer of 0 to 50, its average        being within a range of 0 to 15),    -   a biphenol represented by the following formula (XVIII):        (wherein R¹⁸s each represent a hydrogen atom, a methyl group or        an ethyl group and may be all the same or different from one        another) and    -   a bisphenol represented by a formula (XIX):        (wherein R¹⁹s each represent a hydrogen atom, an alkyl group        having 1 to 10 carbon atoms, an alkoxyl group having 1 to 10        carbon atoms, an aryl group having 6 to 10 carbon atoms, an        aryloxy group having 6 to 10 carbon atoms or halogen and may be        all the same or different from one another, and Y represents an        alkylidene having 1 to 10 carbon atoms, an alkylene having 2 to        10 carbon atoms, a cycloalkylidene having 3 to 10 carbon atoms,        a cycloalkylene having 3 to 10 carbon atoms or a divalent group        such as —O—, —CO—, —CO₂—, —S—, —SO—or —SO₂—),    -   epoxy resins obtained by epoxidating amino groups of aromatic        polyamines such as 4,4′-diaminophenylmethane,        4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone,        2,2′-bis(4,4′-diaminophenyl)propane, m-xylylenediamine,        pxylylenediamine and an aralkyl aniline resin represented by the        following formula (XX):        (wherein R²⁰s each represent a hydrogen atom, a halogen atom, a        linear, branched or cyclic aliphatic alkyl group having 1 to 8        carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a        phenyl group, and n which is the number of recurring-units        represents an integer of 0 to 50, its average being within a        range of 0 to 15), and    -   epoxy compounds or resins derived from aminophenols such as        m-aminophenol, p-aminophenol,        2-(4-aminophenyl)-2-(4′-hydroxyphenyl)propane and        4-aminophenyl-(4′-hydroxyphenyl)-methane.

More preferable of these are epoxy resins or compounds obtained byepoxidating a phenol novolac resin, a phenol dicyclopentadiene resin, aphenol aralkyl resin, a naphthol aralkyl resin, a biphenol and abisphenol.

In the epoxy resin composition of the present invention, as the curingagent as the component (B), any phenolic-hydroxyl-group-containingcompounds or resins 0 to 100 mol % of the hydroxyl groups of which havebeen esterified by acyl groups and ester derivatives thereof can beused.

Firstly, preferable examples of the curing agent (B) include a novolacresin represented by the following formula (VIII) or an ester derivativethereof, a phenol-dicyclopentadiene resin represented by the followingformula (IX) or an ester derivative thereof, a phenol aralkyl resinrepresented by the following formula (X) or an ester derivative thereof,a naphthol aralkyl resin represented by the following formula (XI) or anester derivative thereof, a biphenol compound represented by thefollowing formula (XII) or an ester derivative thereof, or a bisphenolcompound represented by the following formula (XIII) or an esterderivative thereof:

(wherein R⁸s each represent a hydrogen atom, a methyl group or an ethylgroup; n which is the number of recurring units represents an integer of0 to 50, its average being within a range of 0 to 15; and A eachrepresents a hydrogen atom in the case of the compound (B1) and anaromatic acyl group in the case of the compound (B2)),

(wherein R⁹s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹⁰s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹¹s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹²s each represent a hydrogen atom, a methyl group or an ethylgroup and may be all the same or different from one another; and each Arepresents a hydrogen atom in the case of the compound (B1) and anaromatic acyl group in the case of the compound (B2)), and

(wherein R¹³s each represent a hydrogen atom, an alkyl group having 1 to10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms, an arylgroup having 6 to 10 carbon atoms, an aryloxy group having 6 to 10carbon atoms or halogen and may be all the same or different from oneanother; Y represents an alkylidene having 1 to 10 carbon atoms, analkylene having 2 to 10 carbon atoms, a cycloalkylidene having 3 to 10carbon atoms, a cycloalkylene having 3 to 10 carbon atoms or a divalentgroup such as —O—, —CO—, —CO₂—, —S—, —SO—or —SO₂—; and each A representsa hydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)).

Particularly preferable examples of the curing agent (B) include:

-   -   a phenol novolac resin represented by the following formula        (XIV):        (wherein R ¹⁴s each represent a hydrogen atom, a methyl group or        an ethyl group, and n which is the number of recurring units        represents an integer of 0 to 50, its average being within a        range of 0 to 15),    -   a phenol-dicyclopentadiene resin represented by the following        formula (XV):        (wherein R¹⁵s each represent a hydrogen atom, a halogen atom, a        linear, branched or cyclic aliphatic alkyl group having 1 to 8        carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a        phenyl group, and n which is the number of recurring units        represents an integer of 0 to 50, its average being within a        range of 0 to 15),    -   a phenol aralkyl resin represented by the following formula        (XVI):        (wherein R¹⁶s each represent a hydrogen atom, a halogen atom, a        linear, branched or cyclic aliphatic alkyl group having 1 to 8        carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a        phenyl group, and n which is the number of recurring units        represents an integer of 0 to 50, its average being within a        range of 0 to 15),    -   a naphthol aralkyl resin represented by the following formula        (XVII):        (wherein R¹⁷s each represent a hydrogen atom, a halogen atom, a        linear, branched or cyclic aliphatic alkyl group having 1 to 8        carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a        phenyl group or a hydroxyl group, and n which is the number of        recurring units represents an integer of 0 to 50, its average        being within a range of 0 to 15),    -   a biphenol represented by the following formula (XVIII):        (wherein R¹⁸s each represent a hydrogen atom, a methyl group or        an ethyl group and may be all the same or different from one        another), and    -   a bisphenol represented by the following formula (XIX):        (wherein R¹⁹s each represent a hydrogen atom, an alkyl group        having 1 to 10 carbon atoms, an alkoxyl group having 1 to 10        carbon atoms, an aryl group having 6 to 10 carbon atoms, an        aryloxy group having 6 to 10 carbon atoms or halogen and may be        all the same or different from one another, and Y represents an        alkylidene having 1 to 10 carbon atoms, an alkylene having 2 to        10 carbon atoms, a cycloalkylidene having 3 to 10 carbon atoms,        a cycloalkylene having 3 to 10 carbon atoms or a divalent group        such as —O—, —CO—, —CO₂—, —S—, —SO—or —SO₂—).

Esterification of these phenol resins can be performed in accordancewith a known method. Further, an esterifying agent used to esterify theabove hydroxyl groups may be any of an organic carboxylic anhydride, anorganic carboxylic halide and an organic carboxylic acid. A convenientesterifying agent may be selected according to characteristics of anesterifying agent based on the number of carbon atoms of an esterdesired to be derived.

Specific examples of the esterifying agent include acetic anhydride,acetyl chloride, acetyl bromide, acetic acid, propionic anhydride,propionyl chloride, propionyl bromide, propionic acid, butyricanhydride, butyric chloride, butyric acid, valeric anhydride, valericchloride, valeric bromide, valeric acid, pivalic chloride, pivalic acid,phenylacetic acid, phenyl acetyl chloride, 2-phenylpropionic acid,3-phenylpropionic acid, o-tolylacetic acid, m-tolylacetic acid,p-tolylacetic acid, cumenic acid, benzoic anhydride, benzoic chloride,benzoic bromide, benzoic acid, o-methylbenzoic chloride, m-methylbenzoicchloride, p-methylbenzoic chloride, o-methylbenzoic acid,m-methylbenzoic acid, p-methylbenzoic acid, dimethylbenzoic acid, andnaphthoic acid.

These esterifying agents can be used solely or in admixture of two ormore.

Further, in the present invention, the rate of esterification is 0 to100 mol %, preferably 10 to 100 mol %, more preferably 50 to 100 mol %,much more preferably 80 to 100 mol %, most preferably 90 to 100 mol %.

In this regard, an esterification rate of 0% simply implies a phenolcompound or a phenol resin.

In the epoxy resin composition of the present invention, a phenolcompound or phenol resin or an ester derivative thereof is used as thecuring agent for an epoxy resin having two or more functional groups.Since the epoxy resin composition of the present invention is intendedfor use as a thermosetting resin in the same applications as aconventional epoxy-phenol cured product is used, such a combination ofthe constituents that the composition can take a three-dimensionalstructure after cured is desirable.

As for the mixing ratio of the epoxy resin (A) and the curing agent (B),a total of hydroxyl groups and ester groups, that is, active groups, is0.5 to 1.5 mole equivalents, preferably 0.7 to 1.3 mole equivalents,based on 1 mole equivalent of epoxy groups. In actual use, it is morepreferable to adjust and use a molar ratio with which optimum physicalproperties of a cured product can be obtained.

To prepare the epoxy resin composition of the present invention, anytechniques may be used. For example, it is possible that thephosphazenium compound of the formula (1) as the accelerator ismelt-mixed into the curing agent sufficiently in advance and the mixtureis then mixed with the epoxy resin or these may be mixed togethersimultaneously.

Further, to fully homogenize these materials, they may be dry-blended inpowdery form.

In the epoxy resin composition of the present invention, as required, anorganic and/or inorganic filler(s) as a component (D) and otheradditives may be added to the epoxy resin composition.

Particularly, when the epoxy resin composition of the present inventionis used as a sealant for a semiconductor integrated circuit, it isdesirable to use the organic and/or inorganic filler(s) (D) and avariety of additives such as a colorant, e.g. carbon black, a moldreleasing agent, a coupling agent and a flame retardant for the purposesof improving its mechanical properties and reducing an overall cost.

The amount of the organic and/or inorganic filler(s) (D) is preferably100 parts by weight to 1,900 parts by weight based on 100 parts byweight of a total of the epoxy resin (A) and the curing agent (B). Fromthe viewpoints of moisture resistance and mechanical strength, theamount is more preferably not smaller than 250 parts by weight,particularly preferably not smaller 550 parts by weight.

Illustrative examples of the organic and/or inorganic filler(s) (D)include powders such as silica, alumina, silicon nitride, siliconcarbide, talc, calcium silicate, calcium carbonate, mica, clay andtitanium white, and fibers such as glass fibers, carbon fibers andaramid fibers. Of these, crystalline silica and/or fused silica are/ispreferably used in the sealant. Further, in consideration of flowabilityof the resin composition at the time of molding, the silicas desirablyhave spherical shapes or a combination of spherical shapes and irregularshapes.

Further, in the epoxy resin composition of the present invention, inconsideration of mechanical strength and heat resistance, it isdesirable to use a coupling agent to improve adhesion between the resinand the filler. Illustrative examples of the coupling agent include asilane coupling agent, a titanate coupling agent, an aluminate couplingagent and a zircoaluminate coupling agent. Of these, the silane couplingagent is preferable, and particularly, a silane coupling agent having afunctional group which reacts with an epoxy group is the mostpreferable.

Specific examples of such a coupling agent include vinyltrimethoxysilane, vinyl triethoxysilane,N-(2-amino-methyl)-3-aminopropylmethyldimethoxysilane,N-(2-amino-ethyl)-3-aminopropyltrimethoxysilane,3-aminopropyltriethoxysilane, 3-anilinopropyltriethoxysilane,3-glycidoxy-propyltrimethoxysilane,3-glycidoxypropylmethyldimethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-methacryloxypropyltrimethoxysilane, and3-mercaptopropyltrimethoxysilane. These can be used solely or incombination of two or more.

It is desirable that these coupling agents be adsorbed to the surface ofthe filler or solidified by a reaction in advance.

As a method for producing a semiconductor device by sealing asemiconductor integrated circuit by use of the epoxy resin compositionof the present invention, low pressure transfer molding can be said tobe the most commonly used. However, other methods such as injectionmolding, compression molding and cast molding can also be used, and aspecial technique using a solvent can also be used.

Hereinafter, the present invention will be described in detail withreference to Examples. However, the present invention shall not belimited by the Examples in any way.

SYNTHETIC EXAMPLE 1

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 312 g (3 mol) of phenol novolacresin (trade name: BRG#558, product of SHOWA HIGHPOLYMER, hydroxyl groupequivalent: 104 g/eq) was added, and the internal temperature of thecontainer was raised to 125° C. With the internal temperature kept atthe above temperature, 336.9 g (3.3 mol) of acetic anhydride was addeddropwise in two hours under agitation. Thereafter, with the internaltemperature kept at 125° C., the reaction was carried out for 2 hours,and then the temperature was raised to 140° C. At 140 to 150° C., themixture was aged for 2 hours, and then excessive acetic anhydride andby-produced acetic acid were distilled off under a reduced pressure at150° C./10 mmHg at the highest.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 370 g of phenol novolac resin having completely acetylatedhydroxyl groups. Its hydroxyl group equivalent was not smaller than3,000 g/eq (undetectable).

SYNTHESIS EXAMPLE 2

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 312 g (3 mol) of phenol novolacresin (trade name: BRG#558, product of SHOWA HIGHPOLYMER, hydroxyl groupequivalent: 104 g/eq) was added, and the internal temperature of thecontainer was raised to 125° C. With the internal temperature kept atthe above temperature, 421.7 g (3 mol) of benzoyl chloride was addeddropwise in two hours under agitation. A hydrogen chloride gas producedduring the reaction was absorbed into a trap. Thereafter, with theinternal temperature kept at 125° C., the reaction was carried out for 2hours, and then the temperature was raised to 140° C. At 140 to 150° C.,the mixture was aged for 2 hours, and then hydrochloric acid was removedunder a slightly reduced pressure.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 590 g of phenol novolac resin having completely benzoylatedhydroxyl groups. Its hydroxyl group equivalent was not smaller than3,000 g/eq (undetectable).

SYNTHETIC EXAMPLE 3

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 507 g (3 mol) of phenol aralkylresin (trade name: MIREX XLC-4L, hydroxyl group equivalent: 169 g/eq,product of Mitsui Chemicals, Inc.) was added, and the internaltemperature of the container was raised to 125° C. With the internaltemperature kept at the above temperature, 336.9 g (3.3 mol) of aceticanhydride was added dropwise in two hours under agitation. Thereafter,with the internal temperature kept at 125° C., the reaction was carriedout for 2 hours, and then the temperature was raised to 140° C. At 140to 150° C., the mixture was aged for 2 hours, and then excessive aceticanhydride and by-produced acetic acid were distilled off under a reducedpressure at 150° C./10 mmHg at the highest.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 609 g of phenol aralkyl resin having completely acetylatedhydroxyl groups. Its hydroxyl group equivalent was not smaller than3,000 g/eq (undetectable).

SYNTHESIS EXAMPLE 4

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 507 g (3 mol) of phenol aralkylresin (trade name: MIREX XLC-4L, hydroxyl group equivalent: 169 g/eq,product of Mitsui Chemicals, Inc.) was added, and the internaltemperature of the container was raised to 125° C. With the internaltemperature kept at the above temperature, 421.7 g (3 mol) of benzoylchloride was added dropwise in two hours under agitation. A hydrogenchloride gas produced during the reaction was absorbed into a trap.Thereafter, with the internal temperature kept at 125° C., the reactionwas carried out for 2 hours, and then the temperature was raised to 140°C. At 140 to 150° C., the mixture was aged for 2 hours, and thenhydrochloric acid was removed under a slightly reduced pressure.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 785 g of phenol aralkyl resin having completely benzoylatedhydroxyl groups. Its hydroxyl group equivalent was not smaller than3,000 g/eq (undetectable).

SYNTHETIC EXAMPLE 5

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 540 g (3 mol) ofphenol-dicyclopentadiene resin (trade name: DPR-5000, product of MitsuiChemicals, Inc., hydroxyl group equivalent: 180 g/eq) was added, and theinternal temperature of the container was raised to 125° C. With theinternal temperature kept at the above temperature, 336.9 g (3.3 mol) ofacetic anhydride was added dropwise in two hours under agitation.Thereafter, with the internal temperature kept at 125° C., the reactionwas carried out for 2 hours, and then the temperature was raised to 140°C. At 140 to 150° C., the mixture was aged for 2 hours, and thenexcessive acetic anhydride and by-produced acetic acid were distilledoff under a reduced pressure at 150° C./10 mmHg at the highest.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 610 g of phenol-dicyclopentadiene-resin-type resin havingcompletely acetylated hydroxyl groups. Its hydroxyl group equivalent wasnot smaller than 3,000 g/eq (undetectable).

SYNTHESIS EXAMPLE 6

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 540 g (3 mol) ofphenol-dicyclopentadiene resin (trade name: DPR-5000, product of MitsuiChemicals, Inc., hydroxyl group equivalent: 180 g/eq) was added, and theinternal temperature of the container was raised to 125° C. With theinternal temperature kept at the above temperature, 421.7 g (3 mol) ofbenzoyl chloride was added dropwise in two hours under agitation. Ahydrogen chloride gas produced during the reaction was absorbed into atrap. Thereafter, with the internal temperature kept at 125° C., thereaction was carried out for 2 hours, and then the temperature wasraised to 140° C. At 140 to 150° C., the mixture was aged for 2 hours,and then hydrochloric acid was removed under a slightly reducedpressure.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 810 g of phenol-dicyclopentadiene-resin-type resin havingcompletely benzoylated hydroxyl groups. Its hydroxyl group equivalentwas not smaller than 3,000 g/eq (undetectable).

SYNTHETIC EXAMPLE 7

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 654 g (3 mol) of naphtholaralkyl resin (trade name: α-NX-3.2, product of Mitsui Chemicals, Inc.,hydroxyl group equivalent: 218 g/eq) was added, and the internaltemperature of the container was raised to 125° C. With the internaltemperature kept at the above temperature, 336.9 g (3.3 mol) of aceticanhydride was added dropwise in two hours under agitation. Thereafter,with the internal temperature kept at 125° C., the reaction was carriedout for 2 hours, and then the temperature was raised to 140° C. At 140to 150° C., the mixture was aged for 2 hours, and then excessive aceticanhydride and by-produced acetic acid were distilled off under a reducedpressure at 150° C./10 mmHg at the highest.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 745 g of naphthol aralkyl resin having completely acetylatedhydroxyl groups. Its hydroxyl group equivalent was not smaller than3,000 g/eq (undetectable).

SYNTHESIS EXAMPLE 8

To a glass container equipped with a thermometer, an agitator, adropping funnel and a reflux condenser, 654 g (3 mol) of naphtholaralkyl resin (trade name: α-NX-3.2, product of Mitsui Chemicals, Inc.,hydroxyl group equivalent: 218 g/eq) was added, and the internaltemperature of the container was raised to 125° C. With the internaltemperature kept at the above temperature, 421.7 g (3 mol) of benzoylchloride was added dropwise in two hours under agitation. A hydrogenchloride gas produced during the reaction was absorbed into a trap.Thereafter, with the internal temperature kept at 125° C., the reactionwas carried out for 2 hours, and then the temperature was raised to 140°C. At 140 to 150° C., the mixture was aged for 2 hours, and thenhydrochloric acid was removed under a slightly reduced pressure.

The obtained resin was dissolved in 1,400 g of toluene and then washedwith hot water at 60 to 70° C. until waste water becomes neutral, andtoluene was distilled off at 150° C./5 mmHg at the highest so as toobtain 923 g of naphthol aralkyl resin having completely benzoylatedhydroxyl groups. Its hydroxyl group equivalent was not smaller than3,000 g/eq (undetectable).

SYNTHESIS EXAMPLE 9

588 g of phenol novolac resin having 88% of its hydroxyl groupsbenzoylated was obtained in the same manner as in Synthesis Example 2except that the amount of benzoyl chloride was changed to 371.2 g (2.64mol). Its hydroxyl group equivalent was 958 g/eq.

EXAMPLE 1

1 gram equivalent of o-cresol novolac (trade name: EOCN102S-65, productof NIPPON KAYAKU CO., LTD., epoxy equivalent: 210 g/eq) as an epoxyresin and 1 gram equivalent of the acetylated phenol novolac resin(ester equivalent: 146 g/eq=calculated value) of Synthesis Example 1 asa curing agent were fully melt-mixed with each other at 100° C. so as toobtain a homogeneous resin mixture.

To the resin mixture, 0.0055 mol of phosphazenium compound of theforegoing formula (1) wherein R¹ was a methyl group was added as acuring accelerator, and the resulting mixture was mixed at 120° C. for 1minute so as to obtain a resin composition.

To 200 g of the resin composition, a filler and other additives wereadded in the following amounts, and the mixture was roll-mixed underheating so as to obtain a molding material for a sealant:

-   -   Inorganic Filler [Spherical Fused Silica (YXK-35R, product of        TATSUMORI CO., LTD.)]: 1,440 g    -   Silane Coupling Agent (SZ-6083, product of Dow Corning Toray        Silicone Co., Ltd.): 124 g    -   Carnauba Wax: 90 g    -   Carbon Black: 6 g    -   Antimony Oxide: 20 g

Using a portion of the molding material, a cured product was obtainedunder conditions of 175° C./10 min and 150 kg/cm² and then after-curedat 175° C./8 hr (nitrogen atmosphere) so as to fully cure the product.Physical properties were measured by use of the cured product.

Further, by use of the same molding material, test semiconductor deviceswere prepared by low pressure transfer molding, and a cracking test wasconducted by means of a solder bath.

EXAMPLE 2

Tests were conducted in the same manner as in Example 1 except that thecuring agent was changed to the benzoylated phenol novolac resin ofSynthesis Example 2.

EXAMPLE 3

Tests were conducted in the same manner as in Example 1 except that theepoxy compound was changed to YX4000H, the curing agent was changed tothe acetylated phenol aralkyl resin of Synthesis Example 3, and acomposition was obtained by a method comprising the steps of fullymelt-mixing the curing agent with the accelerator at 120° C. in advanceand then adding the epoxy resin.

EXAMPLE 4

Tests were conducted in the same manner as in Example 3 except that thecuring agent was changed to the benzoylated phenol aralkyl resin ofSynthesis Example 4.

EXAMPLE 5

Tests were conducted in the same manner as in Example 1 except that thecuring agent was changed to the acetylated phenol-dicyclopentadieneresin of Synthesis Example 5.

EXAMPLE 6

Tests were conducted in the same manner as in Example 1 except that thecuring agent was changed to the benzoylated phenol-dicyclopentadieneresin of Synthesis Example 6.

EXAMPLE 7

Tests were conducted in the same manner as in Example 3 except that thecuring agent was changed to the acetylated naphthol aralkyl resin ofSynthesis Example 7.

EXAMPLE 8

Tests were conducted in the same manner as in Example 3 except that thecuring agent was changed to the benzoylated naphthol aralkyl resin ofSynthesis Example 8.

COMPARATIVE EXAMPLE 1

A resin composition was prepared in the same manner as in Example 1except that the accelerator was changed to 0.015 mol oftriphenylphosphine. However, a cured product was not obtained. Further,although gelation time was also measured at 150° C. and 200° C. for 20minutes, the test was stopped since no gelation was seen.

COMPARATIVE EXAMPLE 2

A resin composition was prepared in the same manner as in Example 2except that the accelerator was changed to 0.015 mol oftriphenylphosphine. However, a cured product was not obtained. Further,although gelation time was also measured at 150° C. and 200° C. for 20minutes, the test was stopped since no gelation was seen.

COMPARATIVE EXAMPLE 3

Tests were conducted in the same manner as in Comparative Example 1except that the curing agent was changed to a phenol novolac resin(trade name: BRG#558, product of SHOWA HIGHPOLYMER, hydroxyl groupequivalent: 104 g/eq).

COMPARATIVE EXAMPLE 4

Tests were conducted in the same manner as in Comparative Example 1except that the curing agent was changed to aphenol-dicyclopentadiene-resin-type resin (trade name: DPR-5000, productof Mitsui Chemicals, Inc., hydroxyl group equivalent: 180 g/eq).

COMPARATIVE EXAMPLE 5

Tests were conducted in the same manner as in Example 3 except that theaccelerator was changed to 0.015 mol of triphenylphosphine and thecuring agent was changed to a phenol aralkyl resin (trade name: MIREXXLC-4L, hydroxyl group equivalent: 169 g/eq, product of MitsuiChemicals, Inc.).

EXAMPLE 9

Tests were conducted in the same manner as in Example 3 except that thecuring agent was changed to the phenol novolac resin of SynthesisExample 9 having 88% of its hydroxyl groups benzoylated.

EXAMPLE 10

Tests were conducted in the same manner as in Example 3 except that thecuring agent was changed to a mixture of the benzoylated phenol novolacresin of Synthesis Example 2 and a phenol novolac resin (trade name:BRG#558, product of SHOWA HIGHPOLYMER, hydroxyl group equivalent: 104g/eq) at a mixing ratio of 88:12 (ratio of functional groups).

COMPARATIVE EXAMPLE 6

A resin composition was prepared in the same manner as in Example 9except that the accelerator was changed to 0.015 mol oftriphenylphosphine. However, a cured product was not obtained.

COMPARATIVE EXAMPLE 7

A resin composition was prepared in the same manner as in Example 10except that the accelerator was changed to 0.015 mol oftriphenylphosphine. However, a cured product was not obtained.

(Evaluation Results)

The results of the foregoing Examples and Comparative Examples are shownin Tables 1 to 4. Gelation times of the resin compositions prior to theroll mixing were measured at 150° C. Further, physical properties weremeasured in accordance with the following testing methods.

-   -   Tg (Glass Transition Temperature): This was measured in        accordance with a TMA needle penetration method (Shimadzu        TMA-DRW DT-30).    -   Post-Boiling Water Absorption: An increase in weight after        boiled in boiling water of 100° C. for 2 hours was measured.    -   V.P.S Test: Test semiconductor devices were molded and left to        stand in a bath kept at a constant temperature of 85° C. and a        constant humidity of 85% for 168 hours. Immediately after that,        the devices were put in a Fluorinert™ liquid (product of        Sumitomo 3M, FC-70) of 240° C. The number of semiconductors        whose package resins were cracked was counted. The test value        was expressed in the form of a fraction, with a numerator        representing the number of cracked semiconductors and n=5.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Glass Transition Temperature 153148 108 99 129 (° C.) Post-Boiling Water Absorption 0.09 0.16 0.09 0.080.08 (%) V.P.S Test (Rate of Occurrence 0 0 0 0 0 of Cracks (%))Gelation Time (min′ sec″) 4′41″ 5′25″ 5′22″ 5′52″ 4′59″

TABLE 2 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Glass Transition Temperature 119111 105 116 116 (° C.) Post-Boiling Water Absorption 0.10 0.11 0.06 0.100.10 (%) V.P.S Test (Rate of Occurrence 0 0 0 0 0 of Cracks (%))Gelation Time (min′ sec″) 5′56″ 5′42″ 5′30″ 5′35″ 5′31″

TABLE 3 Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5Glass Transition — — 173 141 100 Temperature (° C.) Post-Boiling Water —— 0.21 0.15 0.12 Absorption (%) V.P.S Test (Rate of — — 3 2 1 Occurrenceof Cracks (%)) Gelation Time Not Not 3′38″ 4′41″ 4.37″ (min′ sec″) CuredCured

TABLE 4 Comp. Comp. Ex. 6 Ex. 7 Glass Transition Temperature (° C.) — —Post-Boiling Water Absorption (%) — — V.P.S Test (Rate of Occurrence ofCracks (%)) — — Gelation Time (min′ sec″) Not Not Cured Cured

With reference to the foregoing Examples, curing of the esterifiedphenol resins and the epoxy resins has been described in detail. Anepoxy resin composition containing the accelerator and phosphazeniumcompound of the present invention as essential components and a compoundwhose hydroxyl groups have been esterified by acyl groups as a curingagent has far superior hygroscopicity and is very advantageous in termsof cracking resistance as compared with a conventional epoxyresin/phenol resin cured product. It is thereby understood that theepoxy resin compound is excellent in cracking resistance as a sealant.

Further, it is realized that when triphenylphosphine (TPP) which is aconventional accelerator is used, triphenylphosphine does not cause acuring reaction in portions esterified by acryl groups, as shown byComparative Examples 1 and 2. From this fact, it is understood that theesterified curing agent and the phosphazenium compound are essentialcomponents so as to obtain high physical properties as the sealant inthe present invention.

EXAMPLE 11

1 gram equivalent of o-cresol novolac (trade name: EOCN102S-65, productof NIPPON KAYAKU CO., LTD., epoxy equivalent: 210 g/eq) as an epoxyresin and 1 gram equivalent of phenol novolac resin (trade name:BRG#558, product of SHOWA HIGHPOLYMER, hydroxyl group equivalent: 104g/eq) as a curing agent were fully melt-mixed with each other at 100° C.so as to obtain a homogeneous resin mixture.

To the resin mixture, 0.0055 mol of phosphazenium compound of theforegoing formula (1) wherein all Rs were a methyl group and Z⁻ was ahydroxy anion was added as a curing accelerator, and the resultingmixture was mixed at 80° C. for 1 minute so as to obtain a resincomposition.

To 200 g of the resin composition, a filler and other additives wereadded in the following amounts, and the mixture was roll-mixed underheating so as to obtain a molding material for a sealant:

-   -   Inorganic Filler [Spherical Fused Silica (YXK-35R, product of        TATSUMORI CO., LTD.)]: 1,440 g    -   Silane Coupling Agent (SZ-6083, product of Dow Corning Toray        Silicone Co., Ltd.): 124 g    -   Carnauba Wax: 90 g    -   Carbon Black: 6 g    -   Antimony Oxide: 20 g

Using a portion of the molding material, a cured product was obtainedunder conditions of 150° C.→185° C./5 min, 185° C./5 min and 150 kg/cm²and then after-cured at 185° C./8 hr (nitrogen atmosphere) so as tofully cure the product. Tests were conducted with respect to curingbehavior and the like.

EXAMPLE 12

Tests were conducted in the same manner as in Example 11 except that thecuring agent was changed to a phenol-dicyclopentadiene resin (tradename: DPR-5000, product of Mitsui Chemicals, Inc., hydroxyl groupequivalent: 180 g/eq).

EXAMPLE 13

Tests were conducted in the same manner as in Example 12 except that theepoxy resin was changed to tetramethylbiphenoldiglycidyl ether (tradename: YX4000H, product of JER CO., LTD., epoxy equivalent: 184 g/eq).

EXAMPLE 14

Tests were conducted in the same manner as in Example 13 except that thecuring agent was changed to a naphthol aralkyl resin (trade name:α-NX-3.2, product of Mitsui Chemicals, Inc., hydroxyl group equivalent:218 g/eq).

EXAMPLE 15

Tests were conducted in the same manner as in Example 14 except that thecuring agent was changed to a phenol aralkyl resin (trade name: MIREXXLC-4L, hydroxyl group equivalent: 169 g/eq, product of MitsuiChemicals, Inc.).

EXAMPLE 16

Tests were conducted in the same manner as in Example 11 except that theepoxy resin was changed to a phenol-dicyclopentadiene-resin-type epoxyresin (trade name: EPICHRON HP-7200, product of DAINIPPON INK ANDCHEMICALS, INC., epoxy equivalent: 262 g/eq).

EXAMPLE 17

Tests were conducted in the same manner as in Example 16 except that thecuring agent was changed to a phenol aralkyl resin (trade name: MIREXXLC-4L, hydroxyl group equivalent: 169 g/eq, product of MitsuiChemicals, Inc.).

EXAMPLE 18

Tests were conducted in the same manner as in Example 17 except that theepoxy resin was changed to a phenol-aralkyl-resin-type epoxy resin:MIREX XLC-4L (product of Mitsui Chemicals, Inc., hydroxyl groupequivalent: 169 g/eq) epoxidated in accordance with a conventionalmethod.

EXAMPLE 19

Tests were conducted in the same manner as in Example 11 except that theepoxy resin was changed to a dihydroxynaphthalenediglycidyl ether (tradename: EPICHRON HP4032, product of DAINIPPON INK AND CHEMICALS, INC., 150g/eq).

EXAMPLE 20

Tests were conducted in the same manner as in Example 19 except that theepoxy resin was changed to bisphenol-A-type diglycidyl ether (tradename: EPICOAT 828, product of JER CO., LTD., epoxy equivalent: 184g/eq).

COMPARATIVE EXAMPLE 8

Tests were conducted in the same manner as in Example 11 except that theaccelerator was changed to 0.008 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 9

Tests were conducted in the same manner as in Example 12 except that theaccelerator was changed to 0.008 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 10

Tests were conducted in the same manner as in Example 13 except that theaccelerator was changed to 0.015 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 11

Tests were conducted in the same manner as in Example 14 except that theaccelerator was changed to 0.015 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 12

Tests were conducted in the same manner as in Example 15 except that theaccelerator was changed to 0.015 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 13

Tests were conducted in the same manner as in Example 16 except that theaccelerator was changed to 0.008 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 14

Tests were conducted in the same manner as in Example 17 except that theaccelerator was changed to 0.008 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 15

Tests were conducted in the same manner as in Example 18 except that theaccelerator was changed to 0.008 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 16

Tests were conducted in the same manner as in Example 19 except that theaccelerator was changed to 0.008 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 17

Tests were conducted in the same manner as in Example 20 except that theaccelerator was changed to 0.015 mol of triphenylphosphine (TPP).

COMPARATIVE EXAMPLE 18

Tests were conducted in the same manner as in Example 11 except that theaccelerator was changed to 0.008 mol of 2-undecylimidazole.

COMPARATIVE EXAMPLE 19

Tests were conducted in the same manner as in Example 12 except that theaccelerator was changed to 0.008 mol of 2-undecylimidazole.

COMPARATIVE EXAMPLE 20

Tests were conducted in the same manner as in Example 13 except that theaccelerator was changed to 0.015 mol of 2-methylimidazole.

COMPARATIVE EXAMPLE 21

Tests were conducted in the same manner as in Example 14 except that theaccelerator was changed to 0.015 mol of 2-methylimidazole.

COMPARATIVE EXAMPLE 22

Tests were conducted in the same manner as in Example 15 except that theaccelerator was changed to 0.015 mol of 2-methylimidazole.

COMPARATIVE EXAMPLE 23

Tests were conducted in the same manner as in Example 16 except that theaccelerator was changed to 0.008 mol of 2-undecylimidazole.

COMPARATIVE EXAMPLE 24

Tests were conducted in the same manner as in Example 17 except that theaccelerator was changed to 0.008 mol of 2-undecylimidazole.

COMPARATIVE EXAMPLE 25

Tests were conducted in the same manner as in Example 18 except that theaccelerator was changed to 0.008 mol of 2-undecylimidazole.

COMPARATIVE EXAMPLE 26

Tests were conducted in the same manner as in Example 19 except that theaccelerator was changed to 0.008 mol of 2-undecylimidazole.

(Evaluation Results)

The results of the foregoing Examples and Comparative Examples are shownin Tables 5 to 10. A method for testing curing behavior is as follows.Further, FIG. 1 is a graph showing the curing behavior of an epoxy resincomposition when CURELASTOMETER is used.

-   -   Curing Behavior: This was measured by CURELASTOMETER V model        manufactured by NSC.    -   Mold: P-200 Temperature: 175° C. (fluctuated)    -   Frequency: 100 cycle/min Amplitude Angle: ±1°    -   Amount of Sample: 4.5 g

TABLE 5 Ex. 11 EX. 12 Ex. 13 Ex. 14 Ex. 15 Glass Transition 179 147 138135 119 Temperature (° C.) Flexural Strength 14.9 13.5 12 12.5 12.3(Kgf/mm2) Flexural Elastic Modulus 1500 1540 1670 1610 1650 (Kgf/mm2)Post-Boiling Water 0.16 0.09 0.08 0.11 0.09 Absorption (%) V.P.S Test 00 0 0 0 (Number of Cracks/10) Gelation Time 3′01″ 3′31″ 5′12″ 5′02″5′13″ (min′ sec″) Torque Start tsx 10″ 19″ 1′05″ 1′12″ 1′10″ (min′ sec″)10% Cured t′ c 19″ 34″ 1′24″ 1′41″ 1′31″ (min′ sec″) 90% Cured t′ c2′21″ 3′15″ 2′58″ 3′17″ 3′07″ (min′ sec″)

TABLE 6 EX. 16 EX. 17 Ex. 18 EX. 19 Ex. 20 Glass Transition 158 129 131146 140 Temperature (° C.) Flexural Strength 13.8 13.5 13 13.6 12.2(Kgf/mm2) Flexural Elastic Modulus 1460 1590 1620 1530 1630 (Kgf/mm2)Post-Boiling Water 0.14 0.11 0.12 0.14 0.13 Absorption (%) V.P.S Test 00 0 0 0 (Number of Cracks/10) Gelation Time 3′28″ 3′18″ 3′31″ 3′20″5′22″ (min′ sec″) Torque Start tsx 09″ 11″ 13″ 09″ 1′35″ (min′ sec″) 10%Cured t′ c 22″ 23″ 25″ 21″ 2′07″ (min′ sec″) 90% Cured t′ c 2′55″ 2′45″2′37″ 2′35″ 4′57″ (min′ sec″)

TABLE 7 Comp. Comp. Comp. Comp. Comp. EX. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12Glass Transition 175 145 106 115 102 Temperature (° C.) FlexuralStrength 13.9 13.5 12.2 12.4 13 (Kgf/mm2) Flexural Elastic Modulus 15001500 1550 1540 1540 (Kgf/mm2) Post-Boiling Water 0.22 0.15 0.1 0.1 0.09Absorption (%) V.P.S Test 2 2 1 1 1 (Number of Cracks/10) Gelation Time5′08″ 6′55″ 4′23″ 4′28″ 4′39″ (min′ sec″) Torque Start tsx 18″ 35″ 29″28″ 29″ (min′ sec″) 10% Cured t′ c 23″ 43″ 41″ 39″ 39″ (min′ sec″) 90%Cured t′ c 5′48″ 9′22″ 9′29″ 7′21″ 6′58″ (min′ sec″)

TABLE 8 Comp. Comp. Comp. Comp. Comp. Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17Glass Transition 152 126 129 147 138 Temperature (° C.) FlexuralStrength 12.8 12.8 12.6 12.7 12.3 (Kgf/mm2) Flexural Elastic Modulus1440 1550 1460 1515 1550 (Kgf/mm2) Post-Boiling Water 0.21 0.17 0.180.22 0.13 Absorption (%) V.P.S Test 2 2 2 2 1 (Number of Cracks/10)Gelation Time 5′13″ 6′31″ 6′12″ 5′45″ 4′33″ (min′ sec″) Torque Start tsx17″ 21″ 21″ 29″ 29″ (min′ sec″) 10% Cured t′ c 29″ 31″ 30″ 41″ 41″ (min′sec″) 90% Cured t′ c 5′55″ 6′22″ 16′21″ 6′09″ 6′29″ (min′ sec″)

TABLE 9 Comp. Comp. Comp. Comp. Comp. Ex. 18 Ex. 19 Ex. 20 Ex. 21 Ex. 22Glass Transition 175 144 107 116 104 Temperature (° C.) FlexuralStrength 14.1 13.5 12.3 12.4 12.6 (Kgf/mm2) Flexural Elastic Modulus1480 1510 1550 1530 1510 (Kgf/mm2) Post-Boiling Water 0.21 0.15 0.1 0.090.12 Absorption (%) V.P.S Test 2 2 1 1 1 (Number of Cracks/10) GelationTime 4′25″ 5′22″ 4′37″ 4′45″ 4′41″ (min′ sec″) Torque Start tsx 27″ 38″30″ 26″ (min′ sec″) 23″ 10% Cured t′ c 30″ 40″ 59″ 52″ 51″ 90% Cured t′c 5′13″ 6′18″ 9′45″ 7′11″ 6′45″ (min′ sec″)

TABLE 10 Comp. Comp. Comp. Comp. Ex. 23 Ex. 24 Ex. 25 Ex. 26 GlassTransition Temperature 151 125 127 146 (° C.) Flexural Strength(Kgf/mm2) 12.9 12.8 12.3 13.7 Flexural Elastic Modulus 1410 1470 14901540 (Kgf/mm2) Post-Boiling Water Absorption 0.2 0.15 0.16 0.2 (%) V.P.STest 2 2 1 2 (Number of Cracks/10) Gelation Time (min′ sec″) 4′52″ 5′19″5′22″ 4′55″ Torque Start tsx (min′ sec″) 22″ 25″ 25″ 25″ 10% Cured t′ c(min′ sec″) 33″ 34″ 36″ 35″ 90% Cured t′ c (min′ sec″) 5′25″ 5′31″ 5′18″5′54″

EXAMPLE 21

0.05 g of phosphazene compound of the formula 1 wherein all R1s were amethyl group was dissolved in 100 g of pure water and then boiled at 95°C. for 20 hours and then at 125° C. for 20 hours (in a glass autoclave).Thereafter, conductivity of the water was measured.

COMPARATIVE EXAMPLE 25

Conductivity was measured in the same manner by use of 0.05 g oftris[tris(dimethylamino)phospholanilidene-amino]phosphine oxide in placeof the phosphazene compound of Example 18.

The results of the foregoing Example and Comparative Example are shownin Table 11.

TABLE 11 Ex. 21 Comp. Ex. 25 Processing Temperature 95° C. 125° C. 95°C. 125° C. Conductivity (μs/cm) 100 104 94 413

As is understood from these conductivities, while the essentialphosphazene catalyst in the present invention shows constantconductivity regardless of the processing temperature, thereby inferringit from analogy that the catalyst is stable, the phosphine oxidecompound of the Comparative Example shows that conductivity became overfour times larger as the temperature increased from 95° C. to 125° C.That is, it is assumed that at high temperatures, it produces aconductive material of some type by decomposition. Therefore, it hasbeen found that they have a large difference with respect to electriccharacteristics as a sealant.

Further, as has already been described with reference to Examples, it isunderstood that when a phosphazene compound which is an essentialaccelerator in the present invention is used in a case where a phenolresin is used as a curing agent, improvements in physical propertiessuch as an increase in Tg and lowered moisture absorptivity can berecognized and, what is more, distinctive curing properties can also beseen, as compared with when conventionally used general-purposetriphenylphosphine is used.

That is, the gelation time is significantly reduced, and the timerequired for 90% curing in measurement of an increase in torque alongwith curing by use of the CURELASTOMETER is significantly reduced. Thisleads to a reduction in cost along with a shortened production cycle inindustrial production of a sealant and makes a great contribution froman industrial standpoint.

INDUSTRIAL APPLICABILITY

As described above, the epoxy resin composition obtained by the presentinvention can be used in industrial fields in which the conventionalepoxy resin composition has been used. Particularly, when used as asealant for a semiconductor, it provides a package with better crackingresistance than the conventional epoxy resin/phenol resin cured productdoes.

1. A curing agent composition for an epoxy resin, comprising a compoundas a curing agent (B) which is selected from the group consisting of thefollowing (B1) to (b3): (B1) a phenol compound having two or morehydroxyl functional groups, (B2) a compound in which a hydroxyl group ofa phenol compound having two or more hydroxyl functional groups isesterified with an acyl group, and (B3) a mixture of the compounds (B1)and (B2), and a salt of a phosphazenium compound as a curing accelerator(C) which is represented by the following formula (I):

(wherein R¹s each represent a hydrogen atom, a linear, branched orcyclic alkyl group having 1 to 10 carbon atoms or an aryl or aralkylgroup having 6 to 10 carbon atoms and may be all the same or differentfrom one another; and Z⁻ represents a halogen anion, hydroxy anion,alkoxy anion, aryloxy anion or carboxy anion).
 2. The composition ofclaim 1, wherein R¹s in the formula (1) are each a methyl group or anethyl group.
 3. The composition of claim 1, wherein Z⁻ in the formula(1) is a hydroxy anion.
 4. The composition of claim 1, wherein thecuring agent (B) is a novolac resin represented by the following formula(VIII) or an ester derivative thereof, a phenoldicyclopentadiene resinrepresented by the following formula (IX) or an ester derivativethereof, a phenol aralkyl resin represented by the following formula (X)or an ester derivative thereof, a naphthol aralkyl resin represented bythe following formula (XI) or an ester derivative thereof, a biphenolcompound represented by the following formula (XII) or an esterderivative thereof, or a bisphenol compound represented by the followingformula (XIII) or an ester derivative thereof:

(wherein R⁸s each represent a hydrogen atom, a methyl group or an ethylgroup; n which is the number of recurring units represents an integer of0 to 50, its average being within a range of 0 to 15; and each Arepresents a hydrogen atom in the case of the compound (B1) and anaromatic acyl group in the case of the compound (B2)),

(wherein R⁹s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹⁰s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹¹s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹²s each represent a hydrogen atom, a methyl group or an ethylgroup and may be all the same or different from one another; and each Arepresents a hydrogen atom in the case of the compound (B1) and anaromatic acyl group in the case of the compound (B2)), and

(wherein R¹³s each represent a hydrogen atom, an alkyl group having 1 to10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms, an arylgroup having 6 to 10 carbon atoms, an aryloxy group having 6 to 10carbon atoms or halogen and may be all the same or different from oneanother; Y represents an alkylidene having 1 to 10 carbon atoms, analkylene having 2 to 10 carbon atoms, a cycloalkylidene having 3 to 10carbon atoms, a cycloalkylene having 3 to 10 carbon atoms or —O—, —CO—,—CO₂—, —S—, —SO— or —SO₂—; and each A represents a hydrogen atom in thecase of the compound (B1) and an aromatic acyl group in the case of thecompound (B2)).
 5. An epoxy resin composition comprising: (A) an epoxyresin having two or more epoxy groups in a molecule, (B) a curing agent,and (C) a curing accelerator, wherein the curing agent (B) is a compoundselected from the group consisting of the following (B1) to (B3): (B1) aphenol compound having two or more hydroxyl functional groups, (B2) acompound in which a hydroxyl group of a phenol compound having two ormore hydroxyl functional groups is esterified with an acyl group, and(B3) a mixture of the (B1) and (B2), and the curing accelerator (C) is asalt of a phosphazenium compound which is represented by the followingformula (I):

(wherein R¹s each represent a hydrogen atom, a linear, branched orcyclic alkyl group having 1 to 10 carbon atoms or an aryl or aralkylgroup having 6 to 10 carbon atoms and may be all the same or differentfrom one another; and Z⁻ represents a halogen anion, hydroxy anion,alkoxy anion, aryloxy anion or carboxy anion).
 6. The composition ofclaim 5, wherein R¹s in the formula (1) each represent a methyl group oran ethyl group.
 7. The composition of claim 5, wherein Z⁻ in the formula(1) represents a hydroxy anion.
 8. The composition of claim 5, whereinthe epoxy resin (A) having two or more epoxy groups in a molecule is anovolac epoxy resin represented by the following formula (II), aphenol-dicyclopentadiene epoxy resin represented by the followingformula (III), a phenol-aralkyl-resin epoxy resin represented by thefollowing formula (IV), a naphthol-aralkyl-resin epoxy resin representedby the following formula (V), a biphenol-epoxy-containing epoxy resinrepresented by the following formula (VI) or abisphenol-epoxy-containing epoxy resin represented by the followingformula (VII):

(wherein R²s each represent a hydrogen atom, a methyl group or an ethylgroup, and n which is the number of recurring units represents aninteger of 0 to 50, its average being within a range of 0 to 15),

(wherein R³s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group, and n whichis the number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15),

(wherein R⁴s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group, and n whichis the number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15),

(wherein R⁵s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms, a phenyl group or a glycidylether group, and n which is the number of recurring units represents aninteger of 0 to 50, its average being within a range of 0 to 15),

(wherein R⁶s each represent a hydrogen atom, a methyl group or an ethylgroup and may be all the same or different from one another), and

(wherein R⁷s each represent a hydrogen atom, an alkyl group having 1 to10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms, an arylgroup having 6 to 10 carbon atoms, an aryloxy group having 6 to 10carbon atoms or halogen and may be all the same or different from oneanother, and Y represents an alkylidene having 1 to 10 carbon atoms, analkylene having 2 to 10 carbon atoms, a cycloalkylidene having 3 to 10carbon atoms, a cycloalkylene having 3 to 10 carbon atoms or —O—, —CO—,—CO₂—, —S—, —SO— or —SO₂—).
 9. The composition of claim 5, wherein thecuring agent (B) is a novolac resin represented by the following formula(VIII) or an ester derivative thereof, a phenoldicyclopentadiene resinrepresented by the following formula (IX) or an ester derivativethereof, a phenol aralkyl resin represented by the following formula (X)or an ester derivative thereof, a naphthol aralkyl resin represented bythe following formula (XI) or an ester derivative thereof, a biphenolcompound represented by the following formula (XII) or an esterderivative thereof, or a bisphenol compound represented by the followingformula (XIII) or an ester derivative thereof:

(wherein R⁸s each represent a hydrogen atom, a methyl group or an ethylgroup; n which is the number of recurring units represents an integer of0 to 50, its average being within a range of 0 to 15; and each Arepresents a hydrogen atom in the case of the compound (B1) and anaromatic acyl group in the case of the compound (B2)),

(wherein R⁹s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹⁰s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹¹s each represent a hydrogen atom, a halogen atom, a linear,branched or cyclic aliphatic alkyl group having 1 to 8 carbon atoms, analkoxy group having 1 to 10 carbon atoms or a phenyl group; n which isthe number of recurring units represents an integer of 0 to 50, itsaverage being within a range of 0 to 15; and each A represents ahydrogen atom in the case of the compound (B1) and an aromatic acylgroup in the case of the compound (B2)),

(wherein R¹²s each represent a hydrogen atom, a methyl group or an ethylgroup and may be all the same or different from one another; and each Arepresents a hydrogen atom in the case of the compound (B1) and anaromatic acyl group in the case of the compound (B2)), and

(wherein R¹³s each represent a hydrogen atom, an alkyl group having 1 to10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms, an arylgroup having 6 to 10 carbon atoms, an aryloxy group having 6 to 10carbon atoms or halogen and may be all the same or different from oneanother; Y represents an alkylidene having 1 to 10 carbon atoms, analkylene having 2 to 10 carbon atoms, a cycloalkylidene having 3 to 10carbon atoms, a cycloalkylene having 3 to 10 carbon atoms or —O—, —CO—,—CO₂—, —S—, —SO— or —SO₂—; and each A represents a hydrogen atom in thecase of the compound (B1) and an aromatic acyl group in the case of thecompound (B2)).
 10. The composition of claim 5, containing an organicand/or inorganic filler(s) (D) in an amount of 100 to 1,900 parts byweight based on 100 parts by weight of a total of the epoxy resin (A)having two or more epoxy groups in a molecule and the curing agent (B).11. A cured epoxy resin obtained by heat-curing the epoxy resincomposition of claim
 5. 12. A semiconductor device obtained by sealing asemiconductor integrated circuit by use of the epoxy resin compositionof claim 5.